Distance measurement apparatus

Abstract

A distance measurement apparatus includes a light emission circuit that includes a switch, a capacitor, a light-emitting element, and a protection element. The light emission circuit charges and discharges the capacitor by opening and closing the switch based on a light emission control signal, and enables the light-emitting element to emit light using electric power during discharge by the capacitor. The light emission circuit is configured such that a parasitic inductance of a first circuit is greater than a parasitic inductance of a second circuit, where the first circuit is a circuit in which the switch, the capacitor, and the light-emitting element are connected in series and in a ring shape, and the second circuit is a circuit in which the switch, the capacitor, and the protection element are connected in series and in a ring shape.

What is claimed is: 
     
       1. A distance measurement apparatus that measures a distance to an object based on a reflected wave of light that is emitted from a light source, the distance measurement apparatus comprising:
 a light emission circuit that includes a switch, a capacitor, a light-emitting element, and a protection element, the light emission circuit charges and discharges the capacitor by opening and closing the switch based on a light emission control signal, and the light emission circuit enables the light-emitting element to emit light using electric power during discharge by the capacitor, 
 wherein the light emission circuit is configured such that a parasitic inductance of a first circuit is greater than a parasitic inductance of a second circuit to suppress surge voltage that is generated during discharge of the capacitor and applied to the switch in a case where a pulse length of the light emission control signal is shorter than a dischargeable duration of the capacitor, where
 the first circuit is a circuit in which the switch, the capacitor, and the light-emitting element are connected in series and in a ring shape, and 
 the second circuit is a circuit in which the switch, the capacitor, and the protection element are connected in series and in a ring shape, 
 
 wherein the protection element is connected in parallel to the switch between the power supply and a ground, and 
 wherein the light emission circuit is configured such that the parasitic inductance of the second circuit is less than a parasitic inductance of a third circuit to suppress the surge voltage that is generated during discharge of the capacitor and applied to the switch in the case where the pulse length of the light emission control signal is shorter than the dischargeable duration of the capacitor, where
 the third circuit is a circuit in which the light-emitting element and the protection element are connected in series and in a ring shape. 
 
 
     
     
       2. The distance measurement apparatus according to  claim 1 , wherein:
 a wiring length between the switch and the protection element is shorter than a wiring length between the switch and the light-emitting element. 
 
     
     
       3. The distance measurement apparatus according to  claim 2 , wherein:
 an internal inductance of the protection element is less than an internal inductance of the light-emitting element. 
 
     
     
       4. The distance measurement apparatus according to  claim 3 , further comprising:
 a snubber circuit that is connected to both terminals of the switch. 
 
     
     
       5. The distance measurement apparatus according to  claim 2 , further comprising:
 a snubber circuit that is connected to both terminals of the switch. 
 
     
     
       6. The distance measurement apparatus according to  claim 1 , wherein:
 an internal inductance of the protection element is less than an internal inductance of the light-emitting element. 
 
     
     
       7. The distance measurement apparatus according to  claim 6 , further comprising:
 a snubber circuit that is connected to both terminals of the switch. 
 
     
     
       8. The distance measurement apparatus according to  claim 1 , further comprising:
 a snubber circuit that is connected to both terminals of the switch.